虫洞能够时光倒流,判断能否在回到出发的位置的时候在出发的时候之前。(判断是否存在负环) 初学最短路,尝试着用了三种方法判断: 1、Bellman Ford (令d全部为0,仅用来判断负环) OJ测试得157MS 2、Bellman Ford 结束后再来一轮松弛若松弛成功则存在负环。 235MS 3、Bellman Ford 用队列优化过的SPFA,判断是否存在一个点同队大
题目: While exploring his many farms, Farmer John has discovered a number of amazing wormholes. A wormhole is very peculiar because it is a one-way path that delivers you to its destination at a time t
//最水的模版题,记下来以后忘了可以看看。 //SPFA #include<iostream> #include<cstdio> #include<cstring> #include<queue> using namespace std; const int INF=0x3f3f3f3f; const int maxn=505; int n, m, w, d[maxn], inqueue[ma